Persistent Trigeminal Artery Playing a Protective Role in a Case of Vertebral Artery Dissection and Stenosis

Several fetal anastomoses have been described between the carotid and vertebrobasilar circulations. These anastomoses usually revert while the P1 segment (posterior cerebral artery segment 1) develops. However, these primitive intracranial embryonic anastomes can occasionally persist in adult age. Persistence of the primitive trigeminal artery (PPTA) is the most common of these persistent fetal anastomoses. Although uncommonly identified, knowledge of this structure is crucial for clinicians who analyze cranial imaging. PPTA has been associated with intracranial aneurysms and arteriovenous malformations but it is not very clear whether or not PPTA can also play a protective role in certain cases. We present the case of a 31-year-old female who suffered from a medullary stroke due to vertebral artery dissection and the persistent trigeminal artery (PTA) possibly played an important protective role since blood flow to the brainstem was preserved via a robust collateral flow from the right internal carotid artery (ICA).